/*
 * Copyright (C) 2011 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef BlockStack_h
#define BlockStack_h

#include "Assertions.h"
#include "FastMalloc.h"
#include "Vector.h"

namespace WTF {

    template<typename T>
    class BlockStack {
    public:
        static const size_t blockSize = 4096;
        static const size_t blockLength = blockSize / sizeof(T);

        BlockStack();

        ~BlockStack();

        T *grow();

        void shrink(T *);

        const Vector<T *> &blocks();

    private:
        Vector<T *> m_blocks;
        T *m_spareBlock; // Used to avoid thrash at block boundaries.
    };

    template<typename T>
    BlockStack<T>::BlockStack()
            : m_spareBlock(0) {
    }

    template<typename T>
    BlockStack<T>::~BlockStack() {
        if (m_spareBlock)
            fastFree(m_spareBlock);
        for (size_t i = 0; i < m_blocks.size(); ++i)
            fastFree(m_blocks[i]);
    }

    template<typename T>
    inline const Vector<T *> &BlockStack<T>::blocks() {
        return m_blocks;
    }

    template<typename T>
    T *BlockStack<T>::grow() {
        T *block = m_spareBlock ? m_spareBlock : static_cast<T *>(fastMalloc(blockSize));
        m_spareBlock = 0;

        m_blocks.append(block);
        return block;
    }

    template<typename T>
    void BlockStack<T>::shrink(T *newEnd) {
        ASSERT(newEnd != m_blocks.last() + blockLength);
        m_spareBlock = m_blocks.last();
        m_blocks.removeLast();

        while (m_blocks.last() + blockLength != newEnd) {
            fastFree(m_blocks.last());
            m_blocks.removeLast();
        }
    }

}

using WTF::BlockStack;

#endif
